Integrated microscope providing near-field and light microscopy

Abstract

Apparatus are disclosed that perform, on demand, both near-field microscopy (NFM) and light-microscopy (e.g., bright-field microscopy or phase-contrast microscopy) of a specimen. The apparatus comprises an NFM microscope including an NFM probe, a first condenser lens system that converges a center portion of an illumination-light flux at a first terminus of the NFM probe, and a second condenser lens system that converges an annular portion of the illumination-light flux at a specimen to illuminate the specimen by Kohler illumination. Evanescent light from a distal terminus of the NFM probe passes to a locus on the specimen. Downstream optics capture light transmitted and/or scattered from the specimen from the NFM probe and from the Kohler illumination to produce both a light-microscope image of the specimen and an NFM image of the specimen.

What is claimed is: 
     
       1. An integrated microscope, comprising on an optical axis: (a) an irradiation optical system operable to produce an irradiation-light flux for irradiating a specimen, the irradiation optical system comprising an NFM probe extending along the optical axis and having an entrance terminus and a distal terminus; a first condenser lens system operable to cause a central portion of the irradiation-light flux to converge on the entrance terminus of the NFM probe so as to form an evanescent wave of light from the distal terminus of the probe to a locus on the specimen; and a second condenser lens system operable to cause a peripheral portion of the irradiation light flux to converge at a region on the specimen;   (b) an observation optical system comprising a first observation lens system operable to collect light from the evanescent wave that is scattered or transmitted by the locus on the specimen, and a second observation lens system operable to collect light scattered or transmitted from the region on the specimen; and   (c) a stop defining a central aperture and a coaxial annular aperture, the central and annular apertures being situated so as to produce, from the irradiation light flux, the central and peripheral portions, respectively, of the irradiation light flux.   
     
     
       2. The integrated microscope of claim 1, wherein the NFM probe comprises a scanner. 
     
     
       3. The integrated microscope of claim 2, wherein the scanner comprises a piezo element. 
     
     
       4. The integrated microscope of claim 1, further comprising a light source operable to produce the irradiation light flux and to propagate the irradiation light flux along the optical axis. 
     
     
       5. The integrated microscope of claim 1, wherein the first condenser lens system comprises a first condenser lens and a second condenser lens, and the second condenser lens system comprises the second condenser lens. 
     
     
       6. The integrated microscope of claim 5, wherein the first condenser lens system has a shorter focal length than the second condenser lens system. 
     
     
       7. The integrated microscope of claim 6, wherein the second condenser lens system comprises two positive lenses and the first condenser lens system comprises the second condenser lens system and a third positive lens. 
     
     
       8. The integrated microscope of claim 6, further comprising a stop defining a central aperture and a coaxial annular aperture, the central and annular apertures being situated so as to produce, from the irradiation light flux propagating from the light source, the central and the peripheral portions of the irradiation light flux, respectively. 
     
     
       9. The integrated microscope of claim 8, wherein the third condenser lens spans the central aperture. 
     
     
       10. The integrated microscope of claim 1, wherein the observation optical system comprises, on the optical axis, an objective lens and a beam-splitting prism, the beam-splitting prism being operable to reflect light along a first branch of the optical axis to the first observation lens system and to transmit light along a second branch of the optical axis to the second observation lens system. 
     
     
       11. The integrated microscope of claim 10, wherein the objective lens is operable to form a first primary image of the specimen on the first branch of the optical axis and a second primary image of the specimen on the second branch of the optical axis. 
     
     
       12. The integrated microscope of claim 10, wherein the first observation lens system comprises a photomultiplier situated on the first branch of the optical axis, the photomultiplier being operable to analyze the first primary image. 
     
     
       13. The integrated microscope of claim 10, wherein the second observation lens system comprises a relay lens and an eyepiece lens to permit observation by user of the second primary image. 
     
     
       14. An apparatus for performing near-field microscopy and light microscopy of a specimen, the apparatus comprising on an optical axis: (a) a stop defining a central aperture and a coaxial annular aperture, the stop being operable to produce, from an illumination light flux propagating along the optical axis, a central light flux and an annular light flux coaxial with the central light flux;   (b) a near-field microscope subsystem comprising on the optical axis a first condenser lens system, an NFM probe, an objective lens, and a photosensor, the first condenser lens system being operable to converge the central light flux onto the entrance of the NFM probe, the NFM probe being operable to produce, from the central light flux, evanescent light that passes from a distal terminus of the NFM probe to a locus on the specimen, and the objective lens being operable to produce, from the evanescent light interacting with the locus, an image of the locus analyzable by the photosensor; and   (c) a light-microscope subsystem comprising, as situated on the optical axis, a second condenser lens system operable to converge the annular light flux onto the specimen, the objective lens being further operable to produce a viewable image of a region of the specimen on which the annular light flux is incident.   
     
     
       15. An integrated microscope, comprising on an optical axis: (a) an irradiation optical system comprising a stop defining a central aperture and a coaxial annular aperture, the central aperture being operable to produce, from an illumination-light flux, a central light flux, and the annular aperture being operable to pass, from the illumination-light flux, an annular light flux surrounding the central light flux;   (b) an NFM probe having an entrance end and a distal end, the NFM probe being operable to produce, whenever the distal end is situated closely adjacent a locus on a specimen and a light flux is incident on the entrance end, an evanescent light wave extending from the distal end to the locus;   (c) a first condenser lens system operable to converge the central light flux onto the entrance end of the NFM probe so as to cause the probe to produce an evanescent light wave from the distal end to the locus;   (d) a second condenser lens system operable to converge the annular light flux onto the specimen so as to illuminate a region of the specimen by Kohler illumination; and   (e) an objective lens system operable to form a first image of the locus on the specimen illuminated by the evanescent wave, and to form a second image of the region of the specimen illuminated by the Kohler illumination.   
     
     
       16. The integrated microscope of claim 15, wherein the first condenser lens system comprises a first condenser lens spanning the central aperture and a second condenser lens situated between the stop and the entrance end of the NFM probe. 
     
     
       17. The integrated microscope of claim 16, wherein the second condenser lens comprises a first positive lens and a second positive lens.